Damper blade systems are required in many industrial applications and in almost all commercial, and large residential, HVAC systems. Typically, such damper blade systems are used to control the flow of air through a duct or conduit. In addition, such damper blade systems are often used to simultaneously control the flow of air through a return air duct and a fresh air duct of a HVAC system.
FIG. 1 is a schematic showing such a damper blade system in a conventional HVAC system 10 positioned on a roof 12 of a building 20. HVAC system 10 has a housing 14 in fluid communication with a supply air duct 16 and a return air duct 18, both of which are in fluid communication with the interior of building 20. Housing 14 has a relief air duct (outlet) 22 and a fresh air duct (intake) 24 in fluid communication with the external surroundings. Within housing 14 are a fresh air damper 26 and a return air damper 28, both of which are actuated by a control motor 30. Also within housing 14 are an enthalpy control 32, a mixed air sensor 34, a blower 36, a compressor 38, a relief damper 39, as well as other conventional HVAC elements. A thermostat 40 is located within building 20. Thermostat 40, enthalpy control 32, control motor 30, mixed air sensor 34, and compressor 38 form the basic elements of an electro-mechanical control system 42 for HVAC system 10, as indicated by the dashed line in FIG. 1. In addition, the flow of air through HVAC system 10 is generally indicated by bolded arrows in FIG. 1.
Control motor 30 can actuate fresh air damper 26 to any position between fully closed (all damper blades at 0 degrees with respect to y-axis) and fully open (all damper blades at 90 degrees with respect to y-axis). Similarly, control motor 30 can actuate return air damper 28 to any position between fully closed (all damper blades at 0 degrees with respect to x-axis) and fully open (all damper blades at 90 degrees with respect to x-axis). Preferably, the individual damper blades of fresh air damper 26 rotate in sequence, and the individual damper blades of return air damper 28 rotate in sequence. In addition, control motor 30 preferably actuates fresh air damper system 26 and return air damper 28 in a "slaved" fashion. More particularly, when fresh air damper 26 is fully closed, return air damper 28 is fully open. Similarly, when fresh air damper 26 is fully open, return air damper 28 is fully closed. In addition, if fresh air damper 26 is open to a certain angle (e.g. 30 degrees), return air damper 28 is opened to the complimentary angle (e.g. 60 degrees). The rotation of the damper blades of fresh air damper 26 in sequence, the rotation of the damper blades of return air damper 28 in sequence, and the complimentary actuation of fresh air damper 26 and return air damper 28 are important to operating HVAC system 10 in the most economical manner, as is explained in greater detail below.
As one skilled in the HVAC art will recognize, fresh air damper 26 and return air damper 28, in combination with electro-mechanical control system 42, allow HVAC system 10 to cool in the most economical fashion by minimizing the use of compressor 38. As a first example, suppose the ambient air temperature is 88 degrees, and thermostat 40 calls for cooling. Assume also that the mixed air temperature set point for HVAC system 10, which is the desired temperature of air to be supplied to building 20, is 56 degrees. Enthalpy control 32 senses the relatively warm outside air, energizes compressor 38, and signals control motor 30 to move fresh air damper 26 to the fully closed position. Due to the complimentary actuation of fresh air damper 26 and return air damper 28, return air damper 28 is moved to the fully open position. As a second example using the same conditions except that the ambient temperature is only 60 degrees, enthalpy control 32 senses the relatively cool outside air and signals control motor 30 to move fresh air damper 26 to the fully open position and return air damper 28 to the fully closed position. Compressor 38 is only energized if second stage cooling is required, resulting in electricity cost savings. As a third example using the same conditions except that the ambient temperature is only 45 degrees, enthalpy control 32 senses the cool outside air and signals control motor 30 to open fresh air damper 26. As the ambient 45 degree air enters HVAC system 10, mixed air sensor 34 determines that the ambient air is below the desired set point of 56 degrees. In response, mixed air sensor 34 signals control motor 30 to partially close fresh air damper 26, and partially open return air damper 28, so that the mixed air provided to HVAC system 10 is maintained at 56 degrees. Compressor 38 is therefore never energized, resulting in even higher electricity cost savings.
Several known damper systems have been utilized in HVAC system 10. FIG. 2 illustrates one of these damper systems, damper system 50. Damper system 50 has a fresh air damper 52 and a return air damper 54 in a non-coplanar, 120 degree arrangement, in contrast to the non-coplanar, 90 degree arrangement of fresh air damper 26 and return air damper 28 of FIG. 1. Therefore, damper system 50 is utilized in installations having a fresh air duct with a longitudinal axis generally normal to the y-axis and a return air duct with a longitudinal axis generally normal to the x-axis, as shown in FIG. 2.
Fresh air damper 52 has damper blades 56, 57, and 58. Damper blade 56 has an end 56a and an opposing end 56b (not shown), both of which are rotatably supported in a housing 64 by conventional means, such as a circular shaft on damper blade 56 supported by a bushing within housing 64. Damper blade 57 has ends 57a and 57b (not shown), and damper blade 58 has ends 58a and 58b (not shown), all of which are rotatably supported in housing 64 in an identical manner to the ends of damper blade 56. Return air damper 54 has damper blades 59, 60, 61, 62, and 63. Damper blade 59 has ends 59a and 59b (not shown), damper blade 60 has ends 60a and 60b (not shown), damper blade 61 has ends 61a and 61b (not shown), damper blade 62 has ends 62a and 62b (not shown), and damper blade 63 has ends 63a and 63b (not shown), all of which are rotatably supported in housing 64 in an identical manner to the ends of damper blade 56.
Using various linkage systems, control motor 30 may rotate damper blades 56, 57, and 58 of fresh air damper 52 in sequence; rotate damper blades 59, 60, 61, 62, and 63 of return air damper 54 in sequence; and actuate fresh air damper 52 and return air damper 54 in a complimentary manner. In the exemplary linkage system 66 shown in FIG. 2, the shaft of control motor 30 is fixably coupled to a linkage 30a by a set screw 30b. Linkage 30a is fixably coupled to a damper rod 68 by set screw 30c, and damper rod 68 is pivotally coupled to a damper bracket 70. Damper bracket 70 is fixably coupled to damper blade 59 of return air damper 54. Damper brackets 59c, 60c, 61c, 62c, and 63c are fixably coupled to damper blades 59, 60, 61, 62, and 63, respectively. In addition, damper brackets 59c, 60c, 61c, 62c, and 63c are each pivotally coupled to a damper rod 72. A damper bracket 74 is also fixably coupled to damper blade 59 and pivotally coupled to a damper rod 76. Damper rod 76 is pivotally coupled to a damper bracket 78, and damper bracket 78 is fixably coupled to damper blade 57 of fresh air damper 52. Damper brackets 56c, 57c, and 58c are fixably coupled to damper blades 56, 57, and 58, respectively. In addition, damper brackets 56c, 57c, and 58c are each pivotally coupled to a damper rod 79.
The pivotal coupling of damper rods to damper brackets in linkage system 66 is performed using conventional means. For example, the pivotal coupling of damper rod 76 to damper bracket 78 is accomplished using a bushing member 78a receiving damper rod 76, a set screw 78b fixably securing damper rod 76 within bushing member 78a, a pin 78c having one end fixably coupled to bushing member 78a and an opposing end fixably coupled to a bearing member 78d, and a damper bracket body 78e rotatably supporting bearing member 78d.
As shown in FIG. 2, as control motor 30 rotates in a counter-clockwise direction, damper blades 59, 60, 61, 62, and 63 of return air damper 54 begin to close in sequence, and damper blades 56, 57, and 58 of fresh air damper 52 begin to open in sequence. In addition, linkage system 66 actuates return air damper 54 and fresh air damper 52 in a complimentary manner, as is described above. For example, as shown in FIG. 2, when fresh air damper 52 is closed (all damper blades at 0 degrees with respect to y-axis), return air damper 54 is open (all damper blades at approximately 90 degrees with respect to x-axis).
Damper system 50 is subject to several problems. First, the positions of the linkages, damper rods, and damper brackets of linkage system 66 require precise adjustment during manufacturing so that control motor 30 rotates damper blades 56, 57, and 58 of fresh air damper 52 in sequence; rotates damper blades 59, 60, 61, 62, and 63 of return air damper 54 in sequence; and actuates fresh air damper 52 and return air damper 54 in a complimentary manner. However, if any of the set screws in linkage system 66 ever loosen, such sequential rotation and complimentary actuation is lost. Linkage system 66 is extremely difficult to readjust in the field due to the number of moving parts and the precise adjustment required. Second, even though the linkages, damper rods, and damper brackets of linkage system 66 are typically made of corrosion-resistant materials, some degree of corrosion may still occur over time, and this corrosion may cause sequential rotation problems or complimentary actuation problems. Third, damper system 50 is not typically used in installations requiring damper blades having different widths because such installations require an even more complex linkage system than linkage system 66. This in turn creates a problem when one needs a damper system for a duct having a width not evenly divisible into a number of equal width damper blades.
FIGS. 3A, 3B, and 3C illustrate a second, known damper system 80. As shown in FIGS. 3A and 3B, damper system 80 has a fresh air damper 82 and a return air damper 84 in a coplanar arrangement, in contrast to the non-coplanar, 90 degree arrangement of fresh air damper 26 and return air damper 28 of FIG. 1. Therefore, damper system 80 is utilized in installations having a fresh air duct with a longitudinal axis generally normal to the x-axis and a return air duct with a longitudinal axis generally normal to the x-axis, as shown in FIG. 3A.
Fresh air damper 82 has interlocking damper gears 86, 88, 90, and 92 having hubs 86b, 88b, 90b, and 92b, respectively. Damper blades 86a, 88a, 90a, and 92a (shown as hidden lines) are coupled to damper gears 86, 88, 90, and 92 in a parallel fashion. Damper blades 86a, 88a, 90a, and 92a are also rotatably supported in a housing 102. Return air damper 84 has interlocking damper gears 94, 96, 98, and 100 having hubs 94b, 96b, 98b, and 100b, respectively. Damper blades 94a, 96a, 98a, and 100a (shown as hidden lines) are coupled to gears 94, 96, 98, and 100 in a parallel fashion. Damper blades 94a, 96a, 98a, and 100a are also rotatably supported in a housing 103. All damper gears in damper system 80 are conventional spur gears having the same diameter and the same number of involute gear teeth.
As shown in FIG. 3C, housing 103 has opposing sides 103a and 103b, a top 103c, and a bottom 103d (see FIG. 3A). Damper blade 98a, as well as all other damper blades in return air damper 84, are rotatably supported in housing 103 by bearings 104a and 104b riding within bushings 106a and 106b. Bushing 106a is supported within aperture 108a of side 103a, and bushing 106b is supported within aperture 108b of side 103b. Bearings 104a and 104b are fixably secured to each end of damper blade 98a by set screws 110, welding, or other conventional fastening means. Bearing 104a also extends through hub 98b of damper gear 98. Bearing 104a and damper gear 98 are fixably secured together by a key and mating key shafts (not shown) or other conventional fastening means. Fresh air damper 82 is constructed in an identical manner to return air damper 84, as shown in FIG. 3C.
Returning to FIG. 3A, the motion of fresh air damper 82 is slaved to return air damper 84 by the interlocking of damper gears 86 and 100. In addition, the damper blades of fresh air damper 82 are preferably oriented 90 degrees out of phase with the damper blades of return air damper 84. Therefore, control motor 30 (not shown) actuates fresh air damper 82 and return air damper 84 in a complimentary manner. For example, as shown in FIG. 3A, when fresh air damper 82 is fully open (all damper blades at 90 degrees with respect to x-axis), return air damper 84 is fully closed (all damper blades at 0 degrees with respect to x-axis). As another example, as shown in FIG. 3B, if fresh air damper 82 is open to 30 degrees with respect to the x-axis, return air damper 84 is opened to the complimentary angle of 60 degrees with respect to the x-axis. Contrary to damper system 50, damper system 80 rotates adjacent damper blades in opposite, rather than identical, directions.
Damper system 80 reduces the above-described precision adjustment problems common to damper system 50. However, in order for fresh air damper 82 and return air damper 84 to actuate in a complimentary manner, as is preferred, damper system 80 requires damper blades 86a, 88a, 90a, 92a, 94a, 96a, 98a, and 100a to all have equal widths. More specifically, damper gears 86, 88, 90, 92, 94, 96, 98, and 100 must have the same number of teeth. If the damper gears had varying numbers of teeth, the damper gears, and their associated damper blades, would rotate at different rates. According to conventional mating gear tooth design, damper gears with the same number of teeth generally have the same diameter. Therefore, the interlocking of constant diameter damper gears results in equal width damper blades. As discussed above, this in turn creates a problem when one needs a damper system for a duct having a width not evenly divisible into a number of equal width damper blades.
Damper system 80 has an additional limitation. Even though a given damper system 80 requires that all damper blades have an equal width, different installations of damper system 80 may require varying damper blade widths. Such different installations thus require damper gears of varying diameters. The die required to cast a particular diameter of damper gear typically costs on the order of $15,000. Therefore, damper system 80 is often limited to high volume installations requiring large numbers of gears so that the cost of the die can be spread over many gears.
It is therefore an object of the present invention to provide an improved damper system for positioning proximate to or in a duct which minimizes the number of moving parts and minimizes the degree of precision adjustment required during manufacturing, installation, and maintenance.
It is a firer object of the present invention to provide such a damper system which may use damper blades of varying widths.
It is a further object of the present invention to provide such a damper system which minimizes manufacturing costs by requiring only a single die to cast its damper gears.
It is a further object of the present invention to provide such a damper system having a fresh air damper and a return air damper which are actuated in a complimentary manner.
Still other objects and advantages of the present invention will become apparent to those of ordinary skill in art having reference to the following specification together with its drawings.